In the American West, widespread annual droughts, which were once a rare calamity, have become more frequent and are going to become the “new normal.’’Scientists who work on precipitation trends indicate that prolonged long and severe droughts will be commonplace through the end of the 21 st century. They suggest that extreme droughts are related to global warming from increased greenhouse. If human-induced carbon emissions are not significantly reduced, the American West will face Serious agricultural and water problem.
The records show that an extreme drougnt that can last for many years or even a decade has severe impacts on the ecosystem.The five-year-long drought that hit the American West from 2000 to 2004 had profound consequences for carbon sequestration,agricultural productivity do In the drought’s worst year,crop yields were down by 13 percent. Major river basins showed 5 percent to 50 percent reductions in flow.
By analyzing trends over the last 100 years, scientists see signs of the relationship between warming and drouht in western North America. Evidence suggests that the more frequent drought and low precipition events observed for the West during the 20th centhry are associated with increasing temperatures across the Northern Hemisphere. The Northern Hemisphere has just recorded its 327th consecutive month in which the temperature exceeded the 20th –century average. This year had the fourth- warmest winter on record. More than 3200 heat records were broken in june alone
Most frightening is that the extreme drougtht could becom the new normal: climate models point to a warmer plant, largely because of greenhouse gas emissios. Planetay warming, in turn, is expected to create drier conditions across western North America because of th way global-wind and atmospheric-pressure patterns shift in response.